cargo-fmt in CI and format code

[matthiasbeyer]

This PR adds cargo-fmt in the actions workflows and formats the code, so the lint succeeds.

cargo-fmt configuration is set to default.

[matthiasbeyer]

bors merge

[bors[bot]]

This PR was included in a batch that successfully built, but then failed to merge into master. It will not be retried.

Additional information:

{"message":"At least 1 approving review is required by reviewers with write access.","documentation_url":"https://docs.github.com/articles/about-protected-branches"}

[matthiasbeyer]

Ah yes, the setting was not yet disabled by @philippkeller . Waiting for them to resolve this.

[matthiasbeyer]

bors retry

[bors[bot]]

Build succeeded:

• CI